306 On Malaria. 



France, in Holland, and in many parts of England, and on this conti- 

 nent, in several districts of New England, and in all the middle, west- 

 ern, and southern portions of the United States. 



In vast tracts of France and Italy, where the people are not carri- 

 ed off by violent attacks, the whole population exposed to this dis- 

 ease, under its endless types and varieties, drag on a life of perpetual 

 sickness ; often of incurable intermittents, or a low constantly febrile 

 state, with visceral affections ending in dropsy, or some other fatal 

 termination. "The countenances of these people are sallow, some- 

 times livid, and so emaciated as to give them the appearance of walking 

 spectres." Nor are the effects on their mental condition less remarka- 

 ble. " Apathy, recklessness, indolence, and melancholy," extinguish 

 even the natural desire of improving their condition, or of prolonging 

 their lives. The chronic forms into which this intractable fever runs, 

 vary in intensity, with varying climates. In the temperate regions, 

 such as England, and the United States, as far south as the 40°th of 

 N. lat. they appear in dyspepsia, low spirits, loss of appetite, languor, 

 hypochondria, catarrh, innumerable nervous diseases, and consump- 

 tion. 



n. If the fact is satisfactorily established, that the foregoing dis- 

 eases are produced by pestiferous marsh exhalations, or malaria, it is 

 of importance to ascertain what are its properties, and in what situa- 

 tions, soils, winds, or other phenomena, it has its origin. 



As this destructive influence is not cognizable by our senses, we 

 must rest content in the present state of evidence, with such a con- 

 ception of it as results from weighing probabilities after an attentive 

 examination, and comparison of facts.— If I have quoted, or do here- 

 after quote, extreme cases in support of probabilides, it is because 

 they are conclusive to my mind in settling principles, from which, by 

 analogical induction, parallels may be discovered in different climates, 

 by making due allowance for the difference in quality and amount of 

 materials, and of intensity and duration, in the degrees of heat. 



Chemical analysis has failed to discover malaria in any visible or 

 tangible form, either when escaping, or acting with its greatest malig- 

 nancy. There is an agent, or there are agents developed ox created 

 by the joint action of heat and moisture, aided perhaps by electricity 

 or other subtle powers, upon decaying vegetables, which produce 

 malaria. That these agents are aerial cannot be doubted, because 

 the atmosphere is the medium through which they act. Chemistry, 

 although it has made us acquainted with several deadly gases, which 



